1. Field of the Invention
The present invention relates to a piezoelectric element drive circuit and state detection method, and an image recording device, and particularly, to a technology for detecting a state of a piezoelectric element that uses negative voltage drive.
2. Description of the Related Art
An inkjet printer in which a piezoelectric element is used as a droplet ejection element that discharges droplets is known. In a piezoelectric element drive circuit, switching of high speed, high voltage, and high current is required.
Meanwhile, in an inkjet printer, since a wiring of the droplet ejection element and an ink flow path are closely arranged, short-circuiting of an electrode due to ink leakage may occur.
When high voltage drive is performed in a state in which the electrode is short-circuited, an excessive current flows through a power supply line. Accordingly, damage to a power field effect transistor (FET) in an output stage of the drive circuit or fuse blowout of a protection element occurs, and the drive circuit does not operate normally. Therefore, in a case where short-circuiting occurs in the piezoelectric element, it is necessary for the drive circuit to operate according to appropriate error processing. Therefore, a method of adding a test circuit for determining a state of a load to the drive circuit, and determining a state of the piezoelectric elements prior to a usual operation has been conventionally adopted.
For example, in JP2008-260164A, a state detection device for a recording head, which provides electrical energy to an energy generation element to eject ink, and includes a drive circuit that drives the recording head, a power input terminal that provides power to this drive circuit, a switch having one side connected to the power input terminal, and the other side connected to a power supply, a resistor having one side connected to the power input terminal and the other side connected to the power supply, and detection means for detecting a state of the recording head by observing a voltage of this resistor, is described. According to this device, it is possible to detect the state of the recording head accurately and rapidly without damaging a circuit of a drive system.
However, in a state determination circuit disclosed in JP2008-260164A, since a state detection resistor is inserted between the power supply lines, a power supply is inevitably common to an amplifier and an output boost circuit. Accordingly, in a case where the circuit is adopted in a circuit of a high-speed, large-capacity load, there is a disadvantage in that performance of a push-pull circuit is not sufficiently exhibited and high-speed, large-amplitude drive is limited. Further, there is a problem in that the power supply line becomes unstable due to a flow of a high current.